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authorMatthew Wilcox <mawilcox@microsoft.com>2016-12-14 15:08:49 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-14 16:04:10 -0800
commit148deab223b23734069abcacb5c7118b0e7deadc (patch)
tree56aae9c91802e9262312f7fcbb3571eb9c8ec0e9 /lib
parentb35df27a39f40e39fabf1b1e9569c7b24e1add6a (diff)
downloadlinux-stericsson-148deab223b23734069abcacb5c7118b0e7deadc.tar.gz
radix-tree: improve multiorder iterators
This fixes several interlinked problems with the iterators in the presence of multiorder entries. 1. radix_tree_iter_next() would only advance by one slot, which would result in the iterators returning the same entry more than once if there were sibling entries. 2. radix_tree_next_slot() could return an internal pointer instead of a user pointer if a tagged multiorder entry was immediately followed by an entry of lower order. 3. radix_tree_next_slot() expanded to a lot more code than it used to when multiorder support was compiled in. And I wasn't comfortable with entry_to_node() being in a header file. Fixing radix_tree_iter_next() for the presence of sibling entries necessarily involves examining the contents of the radix tree, so we now need to pass 'slot' to radix_tree_iter_next(), and we need to change the calling convention so it is called *before* dropping the lock which protects the tree. Also rename it to radix_tree_iter_resume(), as some people thought it was necessary to call radix_tree_iter_next() each time around the loop. radix_tree_next_slot() becomes closer to how it looked before multiorder support was introduced. It only checks to see if the next entry in the chunk is a sibling entry or a pointer to a node; this should be rare enough that handling this case out of line is not a performance impact (and such impact is amortised by the fact that the entry we just processed was a multiorder entry). Also, radix_tree_next_slot() used to force a new chunk lookup for untagged entries, which is more expensive than the out of line sibling entry skipping. Link: http://lkml.kernel.org/r/1480369871-5271-55-git-send-email-mawilcox@linuxonhyperv.com Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/radix-tree.c138
1 files changed, 121 insertions, 17 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index dbf4e8c8e100..0a7ac0fb4a65 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -69,6 +69,11 @@ struct radix_tree_preload {
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
+static inline struct radix_tree_node *entry_to_node(void *ptr)
+{
+ return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
+}
+
static inline void *node_to_entry(void *ptr)
{
return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
@@ -1104,6 +1109,120 @@ static inline void __set_iter_shift(struct radix_tree_iter *iter,
#endif
}
+/* Construct iter->tags bit-mask from node->tags[tag] array */
+static void set_iter_tags(struct radix_tree_iter *iter,
+ struct radix_tree_node *node, unsigned offset,
+ unsigned tag)
+{
+ unsigned tag_long = offset / BITS_PER_LONG;
+ unsigned tag_bit = offset % BITS_PER_LONG;
+
+ iter->tags = node->tags[tag][tag_long] >> tag_bit;
+
+ /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
+ if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
+ /* Pick tags from next element */
+ if (tag_bit)
+ iter->tags |= node->tags[tag][tag_long + 1] <<
+ (BITS_PER_LONG - tag_bit);
+ /* Clip chunk size, here only BITS_PER_LONG tags */
+ iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
+ }
+}
+
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+static void **skip_siblings(struct radix_tree_node **nodep,
+ void **slot, struct radix_tree_iter *iter)
+{
+ void *sib = node_to_entry(slot - 1);
+
+ while (iter->index < iter->next_index) {
+ *nodep = rcu_dereference_raw(*slot);
+ if (*nodep && *nodep != sib)
+ return slot;
+ slot++;
+ iter->index = __radix_tree_iter_add(iter, 1);
+ iter->tags >>= 1;
+ }
+
+ *nodep = NULL;
+ return NULL;
+}
+
+void ** __radix_tree_next_slot(void **slot, struct radix_tree_iter *iter,
+ unsigned flags)
+{
+ unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
+ struct radix_tree_node *node = rcu_dereference_raw(*slot);
+
+ slot = skip_siblings(&node, slot, iter);
+
+ while (radix_tree_is_internal_node(node)) {
+ unsigned offset;
+ unsigned long next_index;
+
+ if (node == RADIX_TREE_RETRY)
+ return slot;
+ node = entry_to_node(node);
+ iter->shift = node->shift;
+
+ if (flags & RADIX_TREE_ITER_TAGGED) {
+ offset = radix_tree_find_next_bit(node, tag, 0);
+ if (offset == RADIX_TREE_MAP_SIZE)
+ return NULL;
+ slot = &node->slots[offset];
+ iter->index = __radix_tree_iter_add(iter, offset);
+ set_iter_tags(iter, node, offset, tag);
+ node = rcu_dereference_raw(*slot);
+ } else {
+ offset = 0;
+ slot = &node->slots[0];
+ for (;;) {
+ node = rcu_dereference_raw(*slot);
+ if (node)
+ break;
+ slot++;
+ offset++;
+ if (offset == RADIX_TREE_MAP_SIZE)
+ return NULL;
+ }
+ iter->index = __radix_tree_iter_add(iter, offset);
+ }
+ if ((flags & RADIX_TREE_ITER_CONTIG) && (offset > 0))
+ goto none;
+ next_index = (iter->index | shift_maxindex(iter->shift)) + 1;
+ if (next_index < iter->next_index)
+ iter->next_index = next_index;
+ }
+
+ return slot;
+ none:
+ iter->next_index = 0;
+ return NULL;
+}
+EXPORT_SYMBOL(__radix_tree_next_slot);
+#else
+static void **skip_siblings(struct radix_tree_node **nodep,
+ void **slot, struct radix_tree_iter *iter)
+{
+ return slot;
+}
+#endif
+
+void **radix_tree_iter_resume(void **slot, struct radix_tree_iter *iter)
+{
+ struct radix_tree_node *node;
+
+ slot++;
+ iter->index = __radix_tree_iter_add(iter, 1);
+ node = rcu_dereference_raw(*slot);
+ skip_siblings(&node, slot, iter);
+ iter->next_index = iter->index;
+ iter->tags = 0;
+ return NULL;
+}
+EXPORT_SYMBOL(radix_tree_iter_resume);
+
/**
* radix_tree_next_chunk - find next chunk of slots for iteration
*
@@ -1191,23 +1310,8 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
iter->next_index = (index | node_maxindex(node)) + 1;
__set_iter_shift(iter, node->shift);
- /* Construct iter->tags bit-mask from node->tags[tag] array */
- if (flags & RADIX_TREE_ITER_TAGGED) {
- unsigned tag_long, tag_bit;
-
- tag_long = offset / BITS_PER_LONG;
- tag_bit = offset % BITS_PER_LONG;
- iter->tags = node->tags[tag][tag_long] >> tag_bit;
- /* This never happens if RADIX_TREE_TAG_LONGS == 1 */
- if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
- /* Pick tags from next element */
- if (tag_bit)
- iter->tags |= node->tags[tag][tag_long + 1] <<
- (BITS_PER_LONG - tag_bit);
- /* Clip chunk size, here only BITS_PER_LONG tags */
- iter->next_index = index + BITS_PER_LONG;
- }
- }
+ if (flags & RADIX_TREE_ITER_TAGGED)
+ set_iter_tags(iter, node, offset, tag);
return node->slots + offset;
}